WO2008071039A1

WO2008071039A1 - A data transmission method for orthogonal frequency division multiplexing system

Info

Publication number: WO2008071039A1
Application number: PCT/CN2006/003422
Authority: WO
Inventors: Shuqiang Xia
Original assignee: Zte Corporation
Priority date: 2006-12-15
Filing date: 2006-12-15
Publication date: 2008-06-19
Also published as: US20100303168A1; CN101536377A; EP2104253A4; EP2104253A1; US8121021B2

Abstract

A data transmission method for orthogonal frequency division multiplexing system, concretely includes: in data transmission units with different bandwidth, M OFDM symbols included in each data transmission unit are transmitted, thereinto M being greater than 1, and the character in that: each data transmission unit with different bandwidth transmits two kinds of OFDM symbol with different circular prefix length: OFDM symbol with long circular prefix and OFDM symbol with short circular prefix; and in the data transmission units with different bandwidth, same number of OFDM symbols with long circular prefix and same number of OFDM symbols withshort circular prefix are transmitted.

Description

Data transmission method applied to orthogonal frequency division multiplexing system

Technical field

The present invention relates to the field of broadband wireless communications, and in particular to a data transmission method in the field of orthogonal frequency division multiplexing (OF).

Background technique

Due to its high spectral efficiency, strong anti-multipath interference capability and low implementation cost, OFDM technology has attracted more and more attention and has been promoted as the preferred technology for broadband wireless communication. In the existing OF system, the data transfer method is very important. For a general OFDM system, a plurality of OFDM symbols are included in one data transmission unit (for example, one frame based on an 802.160 FDMA system, a subframe of an LTE 0FDM system, etc.), and each OFDM symbol has a cyclic prefix at the forefront. , it is usually a repetition of a piece of data after the 0FDM symbol. By using the cyclic prefix, the 0FDM system can eliminate inter-symbol interference caused by multipath and maintain the orthogonality between carriers to ensure the spectrum utilization efficiency of the 0FDM system. Therefore, the setting of the cyclic prefix in the data transfer unit is also very important. How to set the cyclic prefix reasonably is of key importance to the 0FDM system. ,

At present, in the 0FDM system, there are two methods for setting the cyclic prefix using the data transfer method.

The first type: "3GPP, TR25. 81, Physical Layer Aspects for Evolved UTRA (release 7)", gives the cyclic prefix setting after the long-term evolution (LTE) of the W-CDMA system to the OFDM system. When seven 0FDM symbols are included in one subframe, the cyclic prefix of the non-word system bandwidth is set as follows:

Cyclic prefix setting in 3GPP, TR25.814.

Bandwidth 1. 25 MHz 2. 5 MHz 5 MHz 10 MHz 15 MHz 20 MHz

(4. 69/9) (4. 69/18) (4. 69/36 (4. 75/73) (4. 73/109) (4. 75/1 cyclic prefix X 6, x 5, ) x 3, x 6, x 2, 46) x 5, setting (5. 21/10 (4. 95/19) (4. 82/37 (4. 82/74) (4. 77/110) (4. 79/1

) χ 1 x 2 ) x 4 x 1 x 5 47) x2 In Table 1, the cyclic prefix setting of 5MHz is taken as an example, "(4. 69/36) x3, (4. 82/37) x 4", indicating that there is a cyclic prefix of 3 OFDM symbols in one subframe. 4. 69us, which is equivalent to 36 sampling points; the cyclic prefix with 4 OFDM symbols is 4. 82us, which is equivalent to 37 sampling points. The cyclic prefix settings for other bandwidths can be analogized. The shortcomings of this method are as follows: As can be seen from Table 1, each bandwidth corresponds to a cyclic prefix setting, and the cyclic prefixes of different bandwidths are mutually incompatible. This incompatibility increases the complexity of the system implementation. Degree, but did not bring gain. In addition, as can be seen from Table 1, there are 8 cyclic prefix lengths in the 6 system bandwidths: 4.69, 5. 21, 4. 95,

4. 82, 4. 75, 4. 73, 4. 77 and 4.79us, users of different bandwidths communicate with each other is a very realistic requirement, which means that each user needs to match 8 kinds when accessing the system. Different cyclic prefixes also increase the time and actual difficulty of the user accessing the system. The second method, see the OFDM system based on the 802.16 standard, but the method mentioned in the system, the cyclic prefix lengths of different bandwidths are the same, and the difference of different cyclic prefixes for different types of data is not considered. In an OFDM communication system, data transmitted by a base station (BS) to a user can be classified into two types: broadcast data and unicast data. Broadcast data refers to data that users should receive within the service range of the base station, such as pilots, important system messages, and so on. When transmitting these messages, the BS needs to ensure that the users with bad channel environment (such as users at the edge of the cell) also receive these important messages correctly. Therefore, the BS should use the 0FDM symbols with long cyclic prefix when sending these messages. The unicast message refers to the data sent by the BS to a certain user. In this case, the BS should use the shorter 0FDM symbol of the cyclic prefix to ensure the efficiency of the system. Therefore, in the existing 0FDM system and standard, when setting the cyclic prefix, the compatibility of different bandwidth cyclic prefix times and the difference of different cyclic prefixes of different types of data are not fully considered, and some only consider a certain Aspects, while ignoring other aspects. Therefore, there is a need to improve the prior art. ' . '

Summary of the invention

The technical problem to be solved by the present invention is to provide a data transmission method applied to an OFDM system, which adopts a new cyclic prefix setting method, satisfies the compatibility of different bandwidth cyclic prefix time lengths, and selects different cyclic prefixes for different types of data. difference.

In order to achieve the object of the present invention, the present invention provides a data transmission method applied to an orthogonal frequency division multiplexing system, which specifically includes: - in different bandwidth data transmission units, transmitting respective data transmission units including M. OFDM symbols (M big 1), characterized in that each data transmission unit of different bandwidth transmits an OFDM symbol with two different cyclic prefix lengths: an OFDM symbol of a long cyclic prefix length and an OFDM symbol of a short cyclic prefix length; 'and a different bandwidth' In the data transfer unit, the same number of long cyclic prefix length OFDM symbols and the same number of short cyclic prefix length OFDM symbols are transmitted.

In the above method, in each data transmission unit, L OFDM symbols with a long cyclic prefix length are transmitted for transmitting broadcast data; and M OFDM symbols with a short cyclic prefix length are transmitted for transmitting unicast data. Where L=1, 2~M-1.

The above method transmits OFDM symbols with long cyclic prefixes at any of the same locations for data transmission units of different bandwidths, such as at the first symbol position of different data transmission units. The method of the invention provides a data transmission method in an orthogonal frequency division multiplexing system, which can simultaneously satisfy the compatibility of different bandwidth cyclic prefix time lengths, and select different cyclic prefix differences of different types of data, which is beneficial to 0FDM. The promotion of technology in the field of broadband wireless communications. : '

BRIEF abstract

Figure 1 is a schematic diagram of the existing cyclic prefix setting in "3GPP, TR25.814".

2 is a schematic diagram of an embodiment of the present invention for setting a cyclic prefix in "3GPP, TR25.814".

BEST MODE FOR CARRYING OUT THE INVENTION

Figure 1 shows the cyclic prefix settings for different bandwidths based on the cyclic prefix settings in Table 1 "3GPP, TR25.814". The vertical bar indicates the symbol with a long cyclic prefix in the subframe; the horizontal bar indicates the shorter 0FDM symbol in the subframe. As can be seen from Figure 1, in each channel bandwidth, there are two symbols of cyclic prefix length in each subframe. In different bandwidth subframes, the number of long (short) 0FDM symbols with different cyclic prefixes is not the same. The length of the long cyclic prefix and the short cyclic prefix is also varied. As mentioned above, the incompatibility of the cyclic prefix length brings great trouble to the implementation of the system and the access of the user.

An embodiment of the present invention is given below based on the OFDM system described in 3GPP, TR 25.816. In the OFDM system described in 3GPP, TR25.814, the sampling rate frequency and the FFT (Fast Fourier Transform) points of different bandwidths are mutually compatible, as shown in Table 2 below: 'Table 2: 3GPP, TR25. Basic parameter setting

5ms。 The OFDM system, the length of a subframe is 0. 5ms. Taking the number of 0FDMAs included in one subframe as seven, we set two cyclic prefix lengths: the longer cyclic prefix length is (10/1.92) us, and the shorter cyclic prefix length is (9/1). 92) us. When setting the cyclic prefix length, you need to consider the following two factors: a. The target application environment of the system, without the application environment, the required cyclic prefix length is also different. For example, for a general mobile communication system, the optimal cyclic prefix length is generally between 4 and 6 us. b. The length of both cyclic prefixes should be an integer multiple of the sample interval corresponding to the lowest bandwidth of the system. The specific selection method belongs to the prior art and will not be described here. ■ And set L=l, that is, in one subframe, one OFDM symbol uses a cyclic prefix with a longer time length; the other six OFDM symbols use a cyclic prefix with a shorter time length. When selecting the value of L, it is more random, and it is of course better to consider the average proportion of data transmitted by the broadcast data in the entire data transfer unit. For example, when the average ratio of broadcast data transmitted by the entire data transfer unit is not more than 1/M, L=l is sufficient.

• When setting the cyclic prefix length and number, you can also use the following method. Let the duration of a data transmission unit be T _D , the length of the 0FDM symbol after deducting the cyclic prefix is T _s , the length of the long cyclic prefix is T _A , and the length of the short cyclic prefix is ^ T _B , L The value should also satisfy the following conditions: ΜΧ Γ + LXT _A + (ML) 乂 T _B = T _D .

According to the above method, the following table gives the cyclic prefix after using the method of the present invention in the 0FDM system described by 3GPP, TR 25.814: Cyclic prefix setting in 3GPP, TR25.814, incorporating the present invention

Figure 2 shows a schematic diagram of the cyclic prefix setting in the 3GPP, TR 25.81 using the present invention. As can be seen from Figure 2 and Table 3, each bandwidth defines two cyclic prefix lengths, and for different bandwidths, Both cyclic prefix lengths are the same. This kind of setting not only considers the compatibility of different bandwidth cyclic prefix time lengths, but also considers the difference of different cyclic prefixes for different types of data, and has many advantages such as simplified implementation and reduced user access time.

It is worth mentioning that it is assumed that the position of the OFDM symbol with a long cyclic prefix in the subframe is fixed. For example, the first symbol of the specified subframe is a long cyclic prefix OFDM symbol, which can also improve the synchronization of the system. Speed and accuracy. Of course, other subframe positions may be specified as long cyclic prefix OFDM symbols, and after the long cyclic prefix OFDM symbol position is determined, the short cyclic prefix 0FDM symbol position is naturally determined. It will be understood by those skilled in the art that the above description is only the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention; The scope of protection of the present invention is covered.

Industrial applicability

The method of the invention provides a data transmission method in an orthogonal frequency division multiplexing system, which can simultaneously satisfy the compatibility of different bandwidth cyclic prefix time lengths, and different types of data using different cyclic prefix differences, which is beneficial to 0FDM. The promotion of technology in the field of broadband wireless communications. ' +

Claims

Claim

A data transmission method applied to an orthogonal frequency division multiplexing system, in which different M data transmission units transmit more than one M OFDM symbols included in respective data transmission units, where M is greater than 1, and its characteristics In that each data transmission unit of different bandwidth transmits an OFDM symbol with two different cyclic prefix lengths: an OFDM symbol of a long cyclic prefix length and an OFDM symbol of a short cyclic prefix length; and the same transmission is performed in a data transmission unit having a different bandwidth The number of long cyclic prefix length OFDM symbols and the same number of short cyclic prefix length OFDM symbols.

2. The method according to claim 1, wherein in each data transfer unit, L OFDM symbols of a long cyclic prefix length are transmitted for transmitting broadcast data; and ML are selected for short cycle prefix length OFDM symbol, used to transmit unicast data; where L=1, 2...M-1.

3. Method according to claim 1 or 2, characterized in that the OFDM symbols with long cyclic prefix are transmitted at any of the same locations for data transmission units of different bandwidths.

4. The method according to claim 3, characterized in that, for data transmission units having different bandwidths, OFDM symbols with long cyclic prefix are transmitted at the first symbol position.

.

5. The method according to claim 4, characterized in that in the OFDM system described in 3GPP, TR 25.814, one OFDM symbol having a long cyclic prefix length of 10/1.92 us is transmitted in each data transfer unit. , and 6 short OFDM symbols with a length of 9/1.92us. . ,

The method according to claim 2, characterized in that the system transmits L OFDM symbols with a long cyclic prefix length according to an average ratio of data transmitted by the entire data transmitting unit of the broadcast data.